1. Field of the Invention
The present invention relates to a transmission, and more particularly to a manual transmission for use in vehicles.
2. Description of the Prior Art
In general, a conventional manual transmission for vehicles comprises a housing which has one and the other longitudinal end walls and has a bottom defining a reservoir for lubricating oil. The other longitudinal end wall of the housing includes an upper wall section and a lower wall section offset from the upper wall section toward the one longitudinal end wall of the housing to define a step surface between the upper and lower wall sections. An input shaft which is adapted to be connected to an output shaft of an engine of a vehicle through a clutch is rotatably supported in the one longitudinal end wall of the housing. A counter shaft extending parallel to the input shaft has one and the other axial ends which are rotatably supported in the one longitudinal end wall of the housing and by a first bearing disposed in the lower wall section of the other longitudinal end wall of the housing, respectively. The counter shaft is connected to the input shaft through an input gear mounted on the inner axial end of the input shaft and a first counter gear mounted on the counter shaft in mesh with the input gear. A chamber is formed in the lower wall section of the other longitudinal end wall of the housing with the first bearing exposed to the chamber. A second bearing is mounted around the counter gear. A second counter gear is mounted around the second bearing for rotation relative to the counter shaft and is in mesh with an output gear mounted on the output shaft.
In the conventional transmission described above, at least a portion of each of the first and second bearings is dipped in the lubricating oil within the reservoir defined at the bottom of the housing, during the half of the rotation of the input shaft. When the input shaft is rotated to cause the counter shaft to be rotated, the lubricating oil within the reservoir is scooped up by the counter gears on the counter shaft and is reduced to such a level that the substantially entire first and second bearings are exposed. During the rotation of the input shaft, the first bearing is lubricated by the lubricating oil adhered to the first bearing prior to the rotation of the input shaft, and by the lubricating oil spattered or splashed on the inner end surface of the first bearing facing the one longitudinal end wall of the housing. However, because the lubricating oil adhered to and spattered on the first bearing is small in quantity, the first bearing is not supplied with a sufficient quantity of lubricating oil, which results in the increase in temperature of the first bearing and also results in the shortness of service life thereof.
In addition, during the rotation of the input shaft, the second bearing is lubricated by the lubricating oil scooped up by the counter gears and dropped on the vicinity of the second bearing. However, because mechanical elements adjacent the second bearing are intimately fitted into and/or engaged with each other for maintaining accuracy, there are an extremely small number of paths or passages along which the lubricating oil dropped on the vicinity of the second bearing is led thereto. Therefore, during the rotation of the input shaft, the second bearing is not supplied with a sufficient quantity of lubricating oil, which results in the increase in temperature of the second bearing and also results in the shortness of service life of the second bearing.